Abstract
Luciferase-immunoprecipitation system (LIPS), a liquid phase immunoassay, was used to evaluate antibody responses directed against the structural proteins of PRRSV in pigs that were experimentally infected with virulent PRRSV strains. First, the viral N protein was used as a model antigen to validate the assay. The LIPS results were highly comparable to that of the commercial IDEXX PRRS X3 ELISA. Subsequently, the assay was applied to simultaneously measure antibody reactivity against all eight structural proteins of PRRSV. The highest immunoreactivities were detected against GP3, M, and N proteins while the lowest reactivity was detected against ORF5a protein. Comparative analysis of the kinetics of antibody appearance revealed that antibodies specific to N protein appeared earlier than antibodies against GP3. Finally, the assay was applied to measure immunoreactivities of clinical serum samples against N and GP3. The diagnostic sensitivity of the LIPS with N protein was superior to that of the LIPS with GP3. Collectively, the results provide additional information about the host antibody response to PRRSV infection.
Highlights
Porcine reproductive and respiratory syndrome virus (PRRSV) is currently circulating in most swine producing countries, causing substantial economic losses [1]
We demonstrated that the Luciferase-immunoprecipitation system (LIPS) can be utilized to simultaneously measure swine antibody responses to multiple proteins of PRRSV
We used a set of antisera collected from pigs before (0 dpi) and at 42 days after they were experimentally infected with different PRRSV strains and their derived mutants [23,32]
Summary
Porcine reproductive and respiratory syndrome virus (PRRSV) is currently circulating in most swine producing countries, causing substantial economic losses [1]. ORF1a and ORF1b comprise approximately 80% of the viral genome and encode for at least 14 non-structural proteins (nsp) that are responsible for replication and transcription of the viral genome [3]. ORF2a, ORF3, and ORF4 encode for three minor glycoproteins GP2, GP3, and GP4, respectively [4,5,6,7] These three minor glycoproteins form heterodimers that are dispensable for viral particle formation but are required for viral infectivity, due to their interaction with CD163, a key receptor for PRRSV entry [8,9,10]. ORF5 and ORF6 respectively encode for GP5 and membrane (M) protein which form heterodimers that are indispensable for viral particle formation [8,11]. ORF2b is embedded within ORF2a and encodes for the envelope (E) protein, an ion-channel protein involved in uncoating of virus and release of the Vaccines 2020, 8, 533; doi:10.3390/vaccines8030533 www.mdpi.com/journal/vaccines
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